The invention relates to an integrated services digital network (hereinafter often referred to as xe2x80x9cISDNxe2x80x9d) terminal adapter, and more particularly to an ISDN terminal adapter that can realize Internet access using a personal computer (hereinafter referred to as xe2x80x9cPCxe2x80x9d) through ISDN communication.
In recent years, a rapidly increasing demand for Internet access has lead to a rapid increase in a shift and a new subscription to ISDN communication by virtue of its advantages including improved access rate and simultaneous utilization of two channels. This also has lead to a rapid increase in demand for a terminal adapter (hereinafter often referred to as xe2x80x9cTAxe2x80x9d) with a built-in digital service unit (hereinafter often referred to as xe2x80x9cDSUxe2x80x9d) that is provided outside the PC body, by virtue of easy setting of various optional functions.
This is because, in order to realize Internet access using PC through ISDN communication, it has hitherto been common practice to use TA with built-in DSU which is provided outside PC. In this case, TA with built-in DSU and PC are connected to each other through an RS-232C cable conforming to V.24 which is physical layer interface standards specified in Telecommunication Standardization Section in International Telecommunication Union (ITU-T). Various optional functions of an analog (A) port and a digital (D) port of TA are set through the RS-232C cable.
In the above construction, optional functions with respect to TA can be easily set. However, wiring within a household is unfavorably complicate due to the form of installation of PC, TA with built-in DSU, and an existing analog telephone connected thereto. Specifically, in many case, in general households, an analog telephone has been disposed at the entrance of a house or in a living room. On the other hand, PC and DSU are not always disposed at the entrance or in the living room and, in many cases, are disposed in a different room provided with a U point interface, such as studies. That is, it is difficult to adopt such a positional relationship that PC and DSU are connected to each other through the RS-232C cable.
More specifically, the ISDN line is one led in the above different room provided with the U point interface where it is connected to TA with built-in DSU which is provided outside PC. Further, TA with built-in DSU in its A port is connected to an analog telephone installed at the entrance or in a living room through the RS-232C cable which has been turned up from the A port. This clearly renders wiring complicate.
A method, which is considered effective for solving this problem, is that DSU is separated from TA and disposed at the entrance or in a living room and the conventional analog telephone on hand is connected to the A port of DSU with DSU being connected to an S/T interface of TA, which has been built in PC, through an S/T interface, thereby simplifying wiring.
In this case, however, optional functions of DSU are set by combining buttons of the analog telephone connected thereto, or by providing a special serial interface on DSU and connecting the special serial interface to PC. Therefore, setting should be performed by connection to a portable PC, such as a notebook-sized PC, rather than PC provided in the separate room. This setting is not easy for users.
When optional functions are set by the analog telephone connected to DSU in its A port, a push button (hereinafter often referred to as xe2x80x9cPBxe2x80x9d) tone signal is output from the analog telephone. In this case, setting functions and setting values are input while consultation with an instruction manual, and, at the same time, setting should be performed while confirming the response from the DSU side through a tone from the telephone receiver. This is troublesome.
Further, it should be noted that, although the rate of increase in the number of subscribers to analog lines has reached the limit, the absolute number of subscribers is as large as 60,000,000 lines. Most of PC users originally use Internet through a modem using the analog communication and, thereafter, shift the analog communication to the ISDN communication according to need.
The invention has been made under the above circumstances, and it is an object of the invention to provide an ISDN terminal adapter that can simplify wiring and, at the same time, is easy to set.
According to the first feature of the invention, an ISDN terminal adapter comprises: a terminal adapter board loaded into a personal computer, the terminal adapter board comprising at least a processing circuit for carrying out modulation-demodulation of a modem and data processing for ISDN and a network controller utilizing the processing circuit as a modem function; and
a digital service unit provided outside the personal computer, the digital service unit comprising a plurality of analog port interfaces and a plurality of S/T interfaces, a set of the analog port interface and the S/T interface being connected to the terminal adapter board and, in addition, performing interfacing with U point of an ISDN line,
various optional functions of the analog port interface in the digital service unit being set by utilizing a tone generation function of the processing circuit in the terminal adapter board through a telephony application interface between a communication application and an operating system (OS).
According to the invention, DSU, which has been built in the TA board in the prior art, is separated from the TA board, an analog telephone is connected to the separated DSU, and various optional functions of the analog port interface (A port) of DSU are set by tone generation functions of the processing circuit of the TA board through a telephony application interface (TAPI) between the communication application and the operating system. By virtue of this construction, various optional functions of the A port in DSU can be set remotely from the personal computer in such a state that a place where DSU and the analog telephone is away from a place where the TA board and the personal computer incorporating it are installed.
In this case, the TA board may comprise: a digital signal processor (DSP) comprising a processing circuit for performing modulation-demodulation of a modem and data processing of ISDN; a first S/T chip connected to the S/T interface is DSU; and a dial access arrangement (DAA) for performing network control for the modem function, the TA board serving to receive analog signals from and transmit analog signals to the A port and to receive digital signals from and transmit digital signals to the S/T interface through DSP connected to an internal bus of the personal computer, tone transmission and tone detection using the modem function of the digital signal processor being performed by utilizing OS of the personal computer.
Further, DSU may comprise: computing means comprising a microprocessor (MPU) that performs setting of protocols and various optional functions of ISDN; a subscriber""s line circuit (SLIC) for interfacing with the TA board; a receiver for receiving and transmitting the tone, the receiver being connected to the subscriber""s line circuit; a gate array (G/A) for interfacing the microprocessor; a module for performing conversion between U point and S/T point with respect to the ISDN line; and a second S/T chip for performing S/T interface connection of S/T point passed through the module to the terminal adapter board.
Furthermore, according to the invention, in order to simplify cable wiring in ordinary households, the TA board and DSU may be connected to each other in such a manner that signal cables for the A port and signal cables for the S/T interface are gathered in a bundle which is seen like a single cable to all appearances.